The present invention relates to a method for monitoring a coordinate-measuring machine and to a coordinate-measuring machine with which the method may be performed.
Modern coordinate-measuring devices use high movement speeds, for example of gantries, so that the measurement performance can be continuously increased. In the process, correspondingly high kinetic energies of moving parts occur, as a result of which the risk of injury to persons, such as operating staff, increases if the machine is intended to remain freely accessible.
It is not always possible to observe the regularly decreasing limit values of the permissible energies due to a reduction in the mass of moving parts. Due to the increasing speeds of moving parts, it is also no longer possible, as with low speeds, to take the available escape option of persons in the case of risk into account in the risk analysis. The only acceptable possibility of solving this problem is to keep the person away from the device or to move the device at only a low speed if persons are present within the danger region.
In machine tools or robots, cost-effective solutions that are typically used are mechanical barriers or cabins for keeping a safe distance between persons and device. If a person must enter the danger region, the relevant devices are shut down to prevent any risk, because these devices can never be entirely safe, even at slow movements, due to their high driving forces.
It is possible to reduce the driving force in small and medium-sized coordinate-measuring machines of portal and horizontal-arm construction such that the risk of injury is reduced and persons can work at the device while the machine is moving. This mode of operation is crucial in metrology, because the presence of the operators at the measuring machine is frequently necessary in the teach-in phase for workpieces or in the case of manual measurements.
In addition to many other solutions for securing a danger region, cameras are used in the prior art.
DE 199 38 639 A1 relates to an apparatus for securing a danger region, in particular the danger region of a device which operates in automated fashion. The apparatus has means for producing an optically monitored virtual barrier and means for producing a switching signal for stopping the device if the barrier is breached. The first means have an image recording unit and a defined target of which the image recording unit records an image. The second means have a comparison unit that compares the recorded image to a variable that is characteristic of a reference image.
DE 100 26 710 A1 relates to an optoelectronic protection device having at least one camera for recording images of a protection region and an evaluation unit, associated therewith, for processing the recorded images and for triggering a reaction in dependence on a detected event. Furthermore provided is at least one radiation source associated with the camera and at least one reflector which limits the protection region.
A disadvantage of these safety installations is that an entire device is considered to be dangerous over the entire movement range of movable parts. If a safety installation is triggered, the device is still slowed down or even shut down, even if this is not necessary in the current situation.
One object of the present invention is that of specifying a solution to this problem. The intention is in particular to specify a method for monitoring a coordinate-measuring machine with which this problem can be solved.